FIG. 1 shows the basic circuit diagram of a battery system 10 which is known from the prior art. The battery system 10 comprises a battery 20 which has a plurality of battery cells 21 which are connected in series. Since the plurality of battery cells 21 are connected in series, the battery system 10 can provide a total voltage of the battery cells 21. The battery system 10 further comprises a plurality of cell monitoring apparatuses (“Cell Supervision Circuits”). A cell monitoring apparatus 30 (CSC) of this kind is in each case electrically connected to the connections (not identified) of one or more battery cells 21 and is configured to detect the respective individual voltages of all the battery cells 21 which are connected to it. A cell monitoring apparatus 30 is further configured to measure the temperature of the battery cells 21 which are connected to it. Other hardware solutions are also feasible for the cell monitoring apparatuses 30 which are illustrated in FIG. 1. Furthermore, a battery system 10 can also comprise circuits for charge equalization of the battery cells 21 (cell balancing) which are generally connected in parallel with the battery cells 21 and are often configured as a constituent part of the cell monitoring apparatuses 30. In order to simplify the illustration from FIG. 1, the circuits for charge equalization of the battery cells 21 are not separately illustrated
A charging and disconnection device 40 is connected between the battery cells 21, which are connected in series, and a positive battery terminal 22. The charging and disconnection device 40 comprises a relay 41 which is connected in parallel with a series circuit comprising a further relay 42 and a charging resistor 43. Furthermore, a disconnection device 50 which is formed from a relay is connected between the battery cells 21, which are connected in series, and the negative battery terminal 23. The disconnection and charging devices 40, 50 are each configured to disconnect the battery cells 21 from the battery terminals 22, 23 in order to thereby remove voltage from the battery terminals 22, 23.
The battery system 10 further comprises a central battery controller (Battery Control Unit) 60 which is configured to control the battery system 10 or the battery 20. The battery controller (BCU) 60 is connected to the cell monitoring apparatuses 30 by means of an internal bus system 70 and is configured to detect the current in the current path of the battery system 10 by means of current sensors 80, 90. Furthermore, the battery controller 60 is configured to drive the relays 41, 42, 50, which are present in the charging and disconnection devices 40, 50, by means of corresponding control lines 100, 110 in each case. The battery controller 60 is also connected to the battery terminals 22, 23 by means of electrical lines 120, 130. The battery controller 60 can further be connected to a vehicle interface by means of a CAN bus system 140.
As shown in FIG. 1, a disconnection device 150 is present in the current path of the battery system 10, it being possible for the said disconnection device to be configured, in particular, as a service plug (“service disconnect”) or as a service socket. To this end, the pins 151, 152 of the service socket are connected by a service plug 153. In this case, the disconnection device 150 is typically configured such that the battery cells 21 can be divided into two separate blocks by this disconnection device 150. The disconnection device 150 is generally fitted to the outside of the battery system 10 and allows, in particular maintenance and servicing work, the battery terminals, that is to say the connections 22, 23 of the battery system 10, to be switched to be free of current and free of voltage in a defined manner by pulling out the service plug 153 in order to be able to work on the vehicle in which the battery system 10 is installed without risk. For this reason, the disconnection device 150 is integrated in the battery system 10 in such a way that the contacts or the connections 151, 152 (pins) of the disconnection device 150 are accessible from outside the battery system 10.
However, since the connections 151, 152 (pins) of the disconnection device 150 are accessible from outside the battery system 10, there is also a possibility of misuse. For example, it is possible, in principle, for third parties to connect additional battery cells or batteries from the outside by means of the connections 151, 152 of the disconnection device 150 when the service plug 153 is removed.
FIG. 2 shows the same battery system 10 as in FIG. 1, wherein, in contrast to FIG. 1, additional battery cells or batteries 160 are connected between the connections 151, 152 of the disconnection device 150. As a result, the total voltage of the battery system 10 and therefore the performance can be increased (so-called “tuning”). However, these externally connected batteries or battery cells 160 are not subject to the voltage and temperature monitoring which is carried out by means of the cell monitoring apparatuses 30. Therefore, calculation of the parameters which are relevant for performance, reliability and safety of the battery system 10, such as the “state of charge”, the age (“state of health”) or the functional state (“state of function”), is no longer possible or is possible only such that it is faulty. Charge equalization of the battery cells 21, that is to say cell balancing of the entire battery system 10, as described above is no longer possible either since the internal calculations are corrupted by the presence of the additionally connected battery cells or batteries 160. Consequently, the service life and the storage capacity of all the battery cells 21 of the battery system 10 fall. In the extreme case, the improper use of the disconnection device 150 described here may even lead to safety-critical situations.
One disadvantage of the conventional battery systems is that manipulation of the connections 151, 152, for example those cited further above, can be identified only with difficulty or great difficulty and therefore are also difficult to avoid. For example, misuse of the disconnection device 150 in the conventional battery system 10 shown in FIGS. 1 and 2 is often not identified even though the total voltage of the battery system or of the battery pack 10 is monitored. This is because, depending on the existing state of charge of the battery 20 which is produced, for example, as a result of the drop in the terminal voltage of the battery cells 21 with a falling state of charge (SOC), the measured total voltage of the battery system 10 is always within a permissible tolerance range. In other words, when the total voltage of the battery system is still within a permissible tolerance range, connection of an external battery 160 to the connections (terminals) 151, 152 of the disconnection device (service disconnect) 150 cannot be identified.
Furthermore, document DE 102 21 086 A1 discloses a control apparatus for a motor vehicle, which control apparatus is mounted on a printed circuit board panel during production. The printed circuit board panel comprises an interface and a plurality of data conductor tracks which are connected to the interface and run within the printed circuit board panel. Data is input into the control unit via the interface and the data conductor tracks. In this case, a printed circuit board is separated from the printed circuit board panel during production in such a way that the control unit remains on the separated printed circuit board, the interface remains on a remainder of the panel, and sectional faces of the data conductor tracks remain in an edge of the printed circuit board. This makes mechanical access to the data conductor tracks and therefore also unauthorized access to the data entered into the control unit considerably more difficult.